1. Field of the Invention
The present invention relates to an organic semiconductor device with a vertical structure. In particular, the invention relates to a composite-type organic semiconductor device having both functions of an organic thin film transistor and a light-emitting element.
2. Description of the Related Art
An organic thin film transistor is a driving element formed by using an organic semiconductor film as an active layer. Since the use of an organic semiconductor material enables reduction in weight, it is expected to be put into practical applications such as a next-generation portable electronic appliance or a large-screen display.
In addition, in an organic thin film transistor with a vertical structure, current flows in the vertical direction of an active layer; therefore, current flowing in the film thickness direction can be controlled, enabling a shorter channel length. Therefore, a large current density and high operating speed can be achieved even in the case of using an organic semiconductor film with high resistance and yet low mobility.
As an organic thin film transistor with a vertical structure, such a structure is known that a meshed gate electrode is sandwiched between organic semiconductor layers that are sandwiched between a pair of electrodes, and a metal material, a conductive high-polymer material or the like is used for the material of the gate electrode (cf. Japanese Patent Laid-Open No. 2004-128028).
However, there are such problems that in the case of forming a gate electrode with a metal material, optimization of a shape for stabilizing the element characteristics is difficult to achieve, while in the case of forming a gate electrode with an organic conductive film such as a conductive high-polymer material, electrical characteristics cannot be controlled sufficiently.
Further, even in the case of a composite-type organic semiconductor device where an organic semiconductor layer of an organic thin film transistor emits light, there is a problem in that the luminance and quantum efficiency cannot be controlled sufficiently.